1. Field of the Invention
This invention relates to protective devices for preventing damage to valves in railway tank cars generally used for carrying various liquid cargoes. More particularly this invention relates to a protective flange used to prevent damage to a valve protruding from the bottom of a tank car.
2. Description of the Prior Art
The Association of Americal Railroads (AAR) railway tank car regulations E9.00 and E10.00 (Appendix E) require that bottom discontinuities which extend radially in excess of one inch beyond the surface of the tank be provided with an approved protective device which in an accident can receive severe impact without producing impact damage to the bottom discontinuity that could permit release of the contents of the tank. Bottom discontinuities are generally projecting parts of sumps, washout nozzles, or bottom outlet types of valves used for draining the tank car.
The usual method for adapting existing tank cars to comply with the AAR requirement was to cut around a non-complying valve on a tank, to remove the valve, and to then secure a combined valve and protective device in the opening left in the tank. Various combined valve and protective device structures may be found in the prior art, as, for example, those shown in U.S. Pat. Nos. 4,180,242; 4,184,663; and 4,394,002. However, the cutting of the tank and the replacement of the valve required by these structures are costly in terms of both time and materials.